Obesity has long been recognized as one of the most frequently occurring late effects after therapy for childhood acute lymphoblastic leukemia (ALL). A number of factors, including exposure to corticosteroids, exposure to cranial irradiation, and diminished exercise capacity reportedly contribute to increased rates of obesity among ALL survivors. The development of obesity during or following ALL treatment places survivors at increased risk for hypertension, type II diabetes, cardiovascular disease, persistent adulthood obesity, and recurrence of cancer. Childhood cancer patients who are already obese at the time of diagnosis represent a particular challenge for the oncologist. Obesity may complicate chemotherapy dose determination. Moreover, treatment-related weight gain may exacerbate the obese patient's already increased risk for many short- and long-term health effects. In view of the growing epidemic of childhood obesity in the general population, understanding the relationship between obesity status at the initiation of ALL therapy and weight gain and associated medical problems both during and following treatment is critically important. Because Hispanic adolescents exhibit exceedingly high rates of obesity, these research questions hold particular relevance to Hispanic Americans. The present study will rely on a historic cohort of 425 pediatric ALL patients treated at one of four institutions that comprise the South Texas Pediatric CCOP between 1990-2000. This patient population, which is 80% Hispanic, provides a unique opportunity to examine the impact of obesity at diagnosis on treatment, survivorship, and subsequent weight gain patterns. Our preliminary findings show that 18% of the patient population was obese and 22% is at risk for obesity at the time of diagnosis. The primary goals of the present study are to: 1) identify risk factors for obesity among ALL patients both during and following completion of chemotherapy; 2) quantify the extent of chemotherapy dose reduction in obese ALL patients; and 3) assess obesity as a prognostic factor in ALL patients.